(a) Field of the Invention
The invention relates to a signal line and a thin film transistor (TFT) array panel for a display device that includes the signal line.
(b) Description of the Related Art
Liquid crystal displays (LCDs) are one of the most widely used types of flat panel displays. Typically, an LCD includes a liquid crystal (LC) layer interposed between two panels provided with field-generating electrodes. The LCD displays images by applying voltages to the field-generating electrodes to generate an electric field in the LC layer. The electric field determines the orientations of the LC molecules in the LC layer to vary light transmittance according to the polarization of incident light.
An LCD including two panels respectively provided with field-generating electrodes, wherein one panel has a plurality of pixel electrodes in a matrix and the other has a common electrode covering the entire surface of the panel, dominates the LCD market.
The LCD displays images by applying a different voltage to each pixel electrode. For this purpose, thin film transistors (TFTs) having three terminals to switch voltages applied to the pixel electrodes, are connected to the pixel electrodes. The TFTs are formed on a thin film transistor array panel. In addition, gate lines to transmit signals for controlling the thin film transistors and data lines to transmit voltages applied to the pixel electrodes are formed on a thin film transistor array panel.
A TFT is a switching element for transmitting the image signals from the data line to the pixel electrode in response to the scanning signals from the gate line.
The TFT is applied to an active matrix organic light emitting display as a switching element for controlling respective light emitting elements.
Currently, chromium (Cr) is conventionally the dominating material for the gate lines and the data lines of a TFT array panel. However, Cr is not an ideal material considering the increasing size trend of LCDs. Since the lengths of the gate and data lines increase along with the LCD size, a material that has a lower resistivity than Cr is desired. Due to its high resistivity, there are limitations to applying Cr to a large LCD.
Copper (Cu) is well known as a low-resistivity substitute for Cr. However, since Cu is sensitive to chemicals, when Cu is applied to signal lines, the signal lines may easily be oxidized and corroded. Furthermore, since organic material tend to condense on a Cu surface, signal lines made with Cu may be easily polluted with organic particles. The oxidation, corrosion, and the pollution may induce a rapid increase of the signal line resistance and degrade process reliability.
A low-resistivity material that can be used to build signal lines in a display device without suffering the above disadvantages of Cu is desired.